Apparatus and process for continuous production of shaped plastic webs



6 7 7., 2 0 J 3 m mw T LNC An T S E Sept. 3, 1963 H. sTElNMANN APPARATUS AND PROCESS FOR PRODUCTION OF SHAPED PLA 2 Sheets-Sheet 1 .n-mdlm Filed Deo. 14, 1960 Vm w WNW.: Bmw E Sept. 3, 1963 H. STEINMANN r-:TAL 3,102,776

APPARATUS ANO PROCESS FOR CONTINUOUS PRODUCTION OF SHAPED PLASTIC WEBS Filed Dec. 14, 1960 2 Sheets-Sheet 2 JLHIUR' v I AI QJ IIIII \\v V N i terial therebetween.

United States APPARATUS AND PROCESS FOR CONTINUOUS v The present invention relates to the continuous production of shaped plastic webs and more particularly to the production of corrugated webs molded-between a pair of coacting endless chain means.

V-It is known to produce shaped plastic webs, sheets,

by employing `hot presses to impart the desired shaping of the web. Where [it is sought to produce shaped plastic Webs of extended lengths, however, the use of hot presses becomes impractical since the pressing apparatus would atent O u foils, and the like, such as for example corrugated webs, i

have to conform to the linear dimensions Y of the web to be shaped. The prohibitive costs involved lin such an attempt `discour-age the production of shaped plastic webs of extended dimensions. Nevertheless, Iit has lalso been proposed to conduct plastic webs continuously through a hot press apparatus whereby the desired shaping of the webs or foils is carried out using pressing form-s and/or pres-sing rollers capable of imparting the desired molded or shaped qualities.

A particular device has been `usedhenetofore `in the forming or molding press consists of two endless bands positioned for rotational movement whereby the web may be passed therebetween during travel of the endless bands along the coacting `portion therebetween. 4ln this connection, the bands move ialong a straight path and are provided along the coacting surfaces thereof with shaped elements `arranged one adjacent the next.` Consequently along passage of the web through the'A straightpath fbetween the coacting endless bands, Ia continuous Waveasurface is imparted to the web by means of the shaped elements. Thus, the pressed portion of one i element is engagingly disposed between the correspondingly adjacent pressed portions of elements carried =by the other endless band. Porthis puipose, the,` elements of one band are staggered with respect to the elements of the other Vband and -a slight interval is provided between i the elements of both bands to accommodate the web ma- Upon suitable heating and subsequent cooling, the shaped or corrugated web maybe `continuously produced during rotation of `the-cooperating endlessbands. i

In particular, with respect to the production 0f corrugated sheets, or foils of plastic materials, devices have been proposed which are provided with axially grooved cylinders or rollers between which the web material is passed so that the desired shaping may -be eiected. Shaping devices, consisting of ia pair of endlessdriven chain bands are also known wherein the web to be shaped is conducted between the cooperating bands in the Well known m-anner. In this instance, the individual sh-apeimparting members are staggered with respect to one U 3,102,776 Patented Sept. 3, 1963 process for the continuous production of shaped plastic a webs molded `between a pair of coacting endless chain means wherein each chain means has shape-imparting means disposing therealong in staggered relation with respect to one another.

It is another object of the present invention to provide for the continuous production of such webs 1while avoiding elongation, stretching-injurious strains and stresses, and the like. i

Other and further objects of the invention will become apparent from the study of the within speciicationiand Iaccompanying drawings in which:

FIG. 1 is a schematic side View of the leading portion 0f ian apparatus in accordance with the invention with certain parts shown in section, `and Y FiG. 2 is a similar view to that of FIG. l illustrating an `alternate embodiment in accordance with the invention. i

In accordance with the present invention, it has been found that an apparatus for the continuous production of shaped plastic webs molded between a pair of coacting endless chain means may be provided which comprises a first and `a second endless Ichain means having a plurality of coacting shape-imparting mea-ns disposed thereon, each of said chain means being mounted for movement on a pair of spaced apart wheels with la corresponding intermediate longitudinal portion of each chain means engaging the other chain means lby means of said shape-imparting means to `achieve the shaping of the web disposed therebetween. One of the wheels is provided as a feed- `ing wheel having its corresponding chain means disposed `thereon so as to receive the incoming web thereat, the shape-imparting means being positioned on the curved Thus, in `the molding treatment of plastic webs to form` `continuous corrugated webs, the web is conductedI between la pair of endless coacting chain means each mounted for movement on a pair of spaced apart sprocket wheels and each having `a plurality of shape-imparting means disposed therealong for resiliently urgingly engaging corresponding shape-imparting means disposed along the other chain means in staggered relation thereto, and

the desired corrugated :shape is conveniently achieved. In i accordance with the invention the web is fed to the peripheral portion vof ione of the chain means mounted Son the leading sprocket wheel therefor at 1a rate` which` maintains the length of the web between adjacent shape-imparting means substantially equal to the peripheral length of the chain means corresponding thereto without` pronounced slack. Thereafter the web is conducted on the chain means Xalong at intermediate longitudinal path in resilient urging engagement between the corresponding shape-imparting means olf the two 'chain Ine-ans -in staggered relation to one another while at the sainetime maintaining the length of the rweb lbetween the adjacent shape imparting means off the chain meains in pronounced slack condition so that the web length along .the straight 1ongitudinal path is equal to the original peripheral length lof the chain means corresponding thereto'at said sprocket v Wheel portion during the feedingnof the web. In this manner, by changing from ia curved to a straight path of travel,

. desired. Y

the web has suii'cient length to cause a slackeningy or dcy mediate longitudinall portion, no undue stretching or deformation will occur and the web will be iree from injurious strains and stresses heretofore encountered in prior operations. In the well-known manner, the plastic web is suitably cooled such as by blowing air thereagainst from above and frombelow to remove the heat supplied to the web in the intermediate longitudinal portion of the endless chain means. Consequently, while the web is heated to conveniently achieve the shaping of the same between the shape-imparting means, the same is thereafter suitably vflxedby cooling. At the same time, the surface ofthe web may be smoothed in accordance with conventional techniques and any after-treatments may be employed as Retterring to the drawing, in FIG. 1, the plastic web or foil `1 passes over the tfeeder rollers 2 in the direction of the arrow and is received along the peripheral portion of the clhlain by shaping rods 3, which are fixedly mounted between chain links 7. Chain links 7 are pivotally interconnected by pivot connectors 5. At the feed position of the plastic web -or foil, the shaping rods 3 are disposed along a curved path in consequence of the mounting ofy the endless chain meansmade up of links 7 on the sprocket wheel 4. r[he ydistance 'between a point in a link 7 and a corresponding point in the next adjacent link`7, or the distance between pivot connectors 5, is delined by t1. The distance l2 is thelength between the radially outermost pointidfone shaping nod 3 and that of the next adjacent shaping rod 3. Thedistance t2 is therefore measured yat a greater yradial distance from the center of the sprocketwheel 4 than Iis the distance t1.` Accordingly the distance The Wehl passes through the intermediate ylongitudinal portion of the coating endless chains between the spaced apart sprocket wheels such that the rods 3 and 6 are maintained in staggered relationship with respect to one Vanother to impart the desired corrugated lshape to the web. By means of guide elements 8 and 9 respectively, the two cooperatingendless chain means are urged resiliently toward one another -so as to abuttingly engage the web k1 therebetween for eiiecting the desired shaping operation. Guide elements 8 and 9 are desirably spring.

mounted in a manner that the same are urged toward one another under an adjustable pressure. Advantageously, guide y.elements 8 and 9 outwardly diverge so as t1 may be considered the distance between respective chain links 7 while the distance t2 may be considered the `distance betwleencorresponding shaping rods 3 at their outermost periphery.

The radial distance from the center of sprocket-Wheel 4 to the 'links 7 of the clhaifn means is defined by r While the to effect a gradual increase at the `feeding'end land decrease at the outlet Vend of the pressure engagement between `the respective endless chains,

With respect to FIGURE 2 a similar embodiment is shown, the difference being rthat in this gure, the shaping rods 3 and 6 are rectangular in cross section rather than circular in cross section in the manner of rods 3 and 6 of FIG. 1. Consequently, the web 1 is shaped in anyangular manner rather than in a continuous waving configuration as shown in FIG. 1. The operation and elements inthis igure correspond to those ofFIG. l.

yThe web during the shape-imparting operation'in the intermediate longitudinal portion may be suitably hea-ted in the well-known manner to aid in :the xing of the shape desired and thereafter the web may be air cooled' and after-treated as desired. l

It will be `appreciated that the chain links V7 are maintained a distance from the center of the sprocket Wheel 4 equal to the radius r while the radially outermost point of the shaping rod 3 or 3 (and accordingly rods Gand 6') is maintained lat a height h labove links 7 and at a radial distance h-l-r vfrom the center of wheel 4. Thus, the distance t2 between a radially outermost point of a rod and that or" the next adjacent rod disposed on the wheel 4 is greater than the corresponding distance r1 of that portion of the chain link 7 defined by a chord -to distance of the outermost peripheral pointot the shaping rods Y3 thereabove is deined by h. Thus, the peripheral point of contact between the Webl 1 and the shaping rods 3 is a radial distance ifrom the center of sprocket wheel 4 equal to the sum of 1j and h.

the difference in length between t2 and t1. Consequently,

the arc described at the distance r between the radii passing from the center of the wheel 4 to the outermost points of the adjacent rods. f

`What 4is claimed is:

` 1. In the process for the molding treatment of plastic webs to form continuous corrugated webs, in which the webis conducted between al pair of endless icoacting chain means each mounted for movementon a pair of spaced apart sprocket wheels and each-having a plurality the distance between corresponding outermost periphenal Wheels. In this connection, the other end of the Lchain made up of links 7 is mounted onka second spnocketvwheel (notV shown) so that the chain will rotate in clock-wise direction .so vas to receive web or ioil 1 andconduct the same through the shaping operation and out the'oppo'site end.v v Y It will be seen from FIG. 1` by closing'up the distance manner la preliminary shaping is achieved without stress andstrain on the web 1. During the further course olf the" web along the longitudinal path corresponding shaping rods 6 disposed on the cooperating chain means made urp of links 10 engage the depressions of web 1 between `adjag cent rods 3. Y Links 10 in the same-manner form an endless` chain mounted on two corresponding spaced Aapart sprocket wheels one orf which ispartially shown and the other `of which is correspondingly positioned adjacentthe other sprocketwheel of the vfirst-"mentioned endless chain.

' .between adjacent shaping rods 3 due to the transition lfrom VIa curvedvpath'to a straight path, the plastic web forms a `depression or slack beween successive rods 3L In this 55 of shape-imparting means disposed vtherealomg for resiliently urgingly engaging corresponding'shape-imparting means disposed along the other chain means in staggered relation thereto to achieve the corrugated shape, the improvement which comprises yfeeding said web to the peripheral portion of one of said chain means mounted on the leading sprocket wheel therefor, Iwithont engagement with the other chain means, at la rate which'm-ain- Y 'tains the length of said web between ladjacent shape-imparting means substantially equal to the peripheral length of the chain means corresponding thereto without pronounced slack, Iandpithereafter conducting the web on said chain means along a longitudinal path in resilient urging engagement between the corresponding .shape-impar-ting means of the two rneans in staggered relation to one another while maintaining the Vlength of said web between the adjacent shapedmparting means of said one chain means in .pronounced slack condition, saidlastmentioned length being substantially equal to the original peripheral length of the chain means corresponding thereto onsaid sprocket wheel during thefeeding.

l2. Improvement according to claim 1 wherein the web is fed .to :a chain means disposed along a curved path having a radius r at 1a peripheral distance h thereabove such that the web` is disposed along a corresponding curved path having a 4radius h-l-r, whereby upon subsequently `conducting said chain means along a longitudinal path, ythe web will Sag between corresponding shapeimparting means disposed along said chain means.

References Cited in the le of this patent UNITED STATES PATENTS 6 Renault May 5, 1942 Atkinson et al. June 13, 1944 Foy Aug. 23, 1953 Segl Nov. 30, 1954 Knowles 1 Sept. 25, 1956 FOREIGN PATENTS Genmany Nov. 13, 1958 Australia Aug. 10, 1959 

1. IN THE PROCESS FOR THE MOLDING TREATMENT OF PLASTIC WEBS TO FORM CONTINUOUS CORRUGATED WEBS, IN WHICH THE WEB IS CONDUCTED BETWEEN A PAIR OF ENDLESS COACTING CHAIN MEANS EACH MOUNTED FOR MOVEMENT ON A PAIR OF SPACED APART SPROCKET WHEELS AND EACH HAVING A PLURALITY OF SHAPE-IMPARTING MEANS DISPOSED THEREALONG FOR RESILIENTLY URGINGLY ENGAGING CORRESPONDING SHAPE-IMPARTING MEANS DISPOSED ALONG THE OTHER CHAIN MEANS IN STAGGERED RELATION THERETO TO ACHIEVE THE CORRUGATED SHAPE, THE IMPROVEMENT WHICH COMPRISES FEEDING SAID WEB TO THE 